Electric lamp and method of manufacture



w. E. KoTscH ELECTRIC LAMP AND METHOD OF" MANUFACTURE Feb. 9, 1 960 2 Sheets-Sheet 1 Filed June 27, 1956 lnven tor Feb. 9, 1960 w. KOTSCH ELECTRIC LAMP AND METHOD OF MANUFACTURE 2 Sheets- Sheet 2 Filed June 27, 1956 Comp/2555 50 Invervtor: WiLLiam E. Kysch b 8 His AI OT e9.

United States Patent ELECTRIC LAMP AND METHOD or MANUFACTURE William E. Kotsch, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application June 27, 1956, Serial No. 594,224

1 Claim. (Cl. 313-279) This invention relates to electric lamps and similar devices, and to a method of manufacture thereof. More particularly, the invention relates to electric lamps of the type having an external stem press through which the lead-in conductors of the lamp are sealed.

' There has recently appeared on the market a baseless type miniature incandescent lamp comprising a small glass bulb provided with an external stem press through which are sealed a pair of pin-type lead-in conductors having rigid outer pin ends which project outwardly from the stem press to serve as the contact terminals for the lamp. lnteriorly of the bulb the lead-in conductors are connected to a filament to support it in place within the bulb and provide the electrical connection thereto. The bulb is exhausted through an exhaust passageway extending through the stem press which passageway, after evacuation and, if desired, gas filling of the bulb, is closed off at its outer end by an exhaust tip to thereby hermetically seal the bulb.

For certain applications, as in the case of miniature lamps operating at voltages (egg. of the order of 12 volts and higher) which require the use of filaments of relatively long length, it is necessary to provide one or more additional supports for the filament in order to properly support the filament in place so as to prevent the sagging and shorting out of the filament and consequent premature failure thereof. Such supplementary support members are generally constituted of short wire lengths which are anchored at one end within the lamp bulb and are provided at their other end with a loop 7 or hook within which the filament is engaged so as to be additionally supported thereby.

While it is possible to anchor such supplementary filament support members on glass beads or insulative bridge members suitably fastened to or mounted on the lead-in conductors of the lamp, such constructions are nevertheless objectionable not only because of the additional manufacturing operations required and resultant added manufacturing costs, but also because of the possibility of cracking of the glass bead during the pressing of the stem press and because of the comparatively large size of bead required by reason of the relatively wide spacing of the lead-in conductors in such pin-type lamps,

such a large size bead preventing or interfering with the insertion of the lamp mount through the small neck of the bulb customarily employed for such pin-type lamps.

It is an object of my invention, therefore, to provide an electric lamp of the type having an external stern press and supplementary support means for the filament thereof and in which the above mentioned objections are obviated.

Another object of my invention is to provide an electric lamp of the external stem press type having supplementary filament support means of simple and inexpensive construction and easy to manufacture.

Still another object of my invention is to provide a novel method of manufacturing an electric lamp of the external stem press type and having a supplementary support for the filamentof the lamp.

Briefly stated, in accordance with one aspect of the invention, an electric lamp of the external stem press type is provided with one or more supplementary filament supports which are embedded in or anchored on the stem press of the lamp. According to another aspect of the invention, the supplementary filament support member is first fused into one end of the exhaust tube of the lamp, and the support member then engaged with the filament of the lamp mount to support it in place prior to the fusion and sealing of the said exhaust tube end and the lamp mount into the neck of the lamp envelope and the ensuing pressing of the softened glass of the envelope neck to form the external stem press of the lamp.

Further objects and advantages of the invention will appear from the following detailed description of a species thereof and from the accompanying drawings.

In the drawing,

Fig. l is an axial section of an electric incandescent lamp comprising my invention, taken in the plane of the stem press thereof.

Fig. 2 is an axial section of the lamp at right angles to the section shown in Fig. 1, i.e., taken normal to the plane of the stem press.

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2.

Figs. 4-8 are views illustrating the successive steps in the manufacture of an electric incandescent lamp according to the method of my invention, and

Figs. 9-12 are views illustrating the successive steps in the manufacture of an electric lamp according to a modified method comprising my invention.

Referring to the drawing, the invention is there illustrated as applied to an electric incandescent lamp of the external stem press type such as disclosed and claimed in co-pending U.S. patent application Serial No. 549,424, Ma-lm et al., filedNovember 28, 1955, and assigned to the assignee of the present invention. Such lamps comprise a sealed glass bulb or envelope 1 provided with a short neck portion 2 terminating in a pinched seal or press portion 3 protruding outwardly from the bulb and through which a plurality (two in the particular case shown) of lead-in conductors 4 are sealed so as to extend parallel to each other in side-by-side relation in the plane of the stern press 3. The lead-in conductors 4 are of the multi-section pin type such as are commonly employed in miniature radio tubes and comprising, in the particular case illustrated, rigid metal outer pin portions 5 and inner lead portions 6 which are hermetically sealed in the stern press 3, the two sections 5 and 6 of each conductor being butt-welded together in endto-end relation. The outer pin portions 5 may be made, for example, of nickel wire having a diameter for instance of ,4, inch. The inner lead portions 6 may be made of conventional Dumet wire commonly employed in the lamp making art for sealing into glass. If desired, however, the conductor 4, instead of being formed of two parts as shown, may be of the conventional threepart type comprising the outer pin portions 5, inner lead portions 6 of copper or nickel, and press lead portions of Dumet. The metal outer pins 5 serve as terminal contacts forthe lamp and for such purpose are embedded at their inner ends in the glass of the stem press- 3 in order to firmly anchor or support the pins in place from the stern press. Interiorly of the envelope 1, the inner leads 6 are connected to the opposite ends of an electrical energy translation element such as a filament 7 comprised, for example, of a wire of tungsten or other suitable refractory metal in coiled or coiled-coil or any other suitable form.

-The envelope. 1v is evacuated and, if dpsired, filled,

with a suitable gas, such as argon, nitrogen or krypton, or mixtures thereof, to a suitable pressure. For such purpose, the stem press portion 3 of the lamp envelope 1 is provided with an exhaust passageway 8 which extends through the stem press at a point between the two conductors 4 and is closed or sealed off at its outer end. The exhaust passageway 8 is constituted by the bore 9 of a glass exhaust tube 10'which is sealed in the stem press 3 and the bore of which is maintained open during the press-forming operation in the manner disclosed and claimed in the aforesaid Malm et al. application Serial No. 549,424, i.e.,' by providing the end portion of the exhaust tube which is fusion-sealed into the stem press 3 with a firmly adherent coating 11 of a suitable inorganic material, such as powdered magnesium oxide or Zirconium oxide, for example, or any of the other coating materials mentioned in the above Malm et al. application, which materials have the property of maintaing the bore of the exhaust tube open during the heating and interfusion of the exhaust tube and the surrounding neck 2 of the lamp bulb 1 and the pressing of the stem press 3; As disclosed in the said co-pending Malm et al. application, the coating material 11 must be one which is chemically inert with respect to the lamp filament 7 at the incandescent operating temperature thereof, and it must have a melting point above that of the glass of which the stern press is constituted, e.g., a melting point above 650 C. in the case of the socalled soft type glasses which are customarily employed for the exhaust tube and the bulb of electric lamps and which have a melting point of around 650 C. In addition, the coating material 11 should also be one which is both physically and chemically stable at temperatures up to at least the temperature (for example, at least 700 C.) which the glass exhaust tube 10 will attain during the tipping-off thereof, otherwise contamination of lamps will occur from the gases or other contaminating impurities introduced in the lamp envelope by unstable coating materials. 7

As shown in Fig. ,1, the filament 7 is additionally supported, at one or more points along its length, by one or more supplementary filament support members 12, only one such supplementary filament support member being shown in the particular case illustrated. The supplementary filament support member 12 is preferably in the form of a length of wire formed of any suitable material, such as molybdenum for instance, and anchored at one end inside the bulb and provided at its other end with a hook or loop 13 within which the filament is engaged so as to be supported thereby. In accordance with the invention, the supplementary filament support member 12 is embedded at one end within the glass of the stem press 3, as shown in Fig. 2, to thereby anchor the support member in place within the bulb.

Referring to Figs. 4-8, illustrating the successive steps in manufacturing an electric incandescent lamp in .the manner according to the invention, a supplementary filament support member or wire 12 is first fused to one end of an exhaust tube 19, which has been previously provided with an internal coating 11, to form an exhaust tube and support wire assembly as shown in Fig. 4. The said assembly of the exhaust tube 10 and support member 12 is then inserted, and supported in a vertical position with its support-carrying end uppermost, in the bore 14 of a supporting jig or head 15 of a lamp mounting machine, with the coated upper end of the exhaust tube protruding above the upper face of the supporting jig. The conductors 4 are also inserted and supported, with their pin end lowermost, within upwardly-opening conductor-receiving apertures or pockets 16 in the supporting jig 15 so as to be held in a vertical position extending alongside the protruding upper end of the exhaust tube 10, in the manner shown in Fig. 5. After placing the assembled exhaust tube and supplementary filament support 12, and the two lead-in conductors 4 in the supporting jig or head 15, a filament 7 is then connected at its ends to the ends of the inner lead portions 6 of the conductors 4. Following the said mounting or attachment of the filament 7 to the lead-in conductors 4, the supplementary filament support member 12 is then formed with a filament-engaging hook portion 13 at its upper end and the said hook portion 13 engaged around the filament, at a point thereof intermediate its connections to the lead-in conductors 4, to thereby additionally support the filament in place. The formation of the hook portion 13 and the engagement and closing thereof around the filament 7 may be performed by conventional type mechanism commonly in use for such purpose in the lampmaking art, such as shown for example in Iden Patent 2,199,852 and co-pending US. application Serial No. 254,052, now Patent No. 2,760,529, Pakish et al., filed October 31, 1951, and assigned to the assignee of the present invention. The engagement of the hook portion 13 of the support member 12 with the filament 7 thus completes the assembly of the lamp mount 17 which is composed of the conductors 4, filament 7 and support member 12.

With the exhaust tube 10 and lamp mount 17 thus positioned in place in the supporting jig or head 15, a glass lamp envelope or bulb 1 is then placed neck end down over the lamp mount and the protruding upper end of the exhaust tube and supported in place on a bulb holder or seat 18 with the neck portion 2 of the bulb surrounding or encircling the protruding upper end of the exhaust tube and the two lead-in conductors 4, in the manner shown in Fig. 7. Gas fires 19 from gas burners 20 are then directed against the neck portion 2 of the bulb 1 to soften the glass forming the said neck portion and collapse it around the lead-in conductors and against the protruding upper end of the exhausttube so as to also soften, by conduction of heat thereto, the glass of the said protruding end of the exhaust tube and interfuse therewith. When the proper degree of heating and softening'of the bulb neck 2 and the protruding upper end of the exhaust tube 10 is attained, a pair of pressforming jaws 21 are then actuated to close against the softened bulb neck about the conductors 4 and against the protruding upper end of the exhaust tube 4, in the manner shown in Fig. 8, to thereby form the stem press 3 of the lamp. During the stem press forming operation, the internal coating 11 in the upper protruding end of the exhaust tube 10 acts to maintain the bore 9 of the exhaust tube open so as to thereafter serve as a passageway 8 for subsequently evacuating the lamp bulb 1.

The formation of the external stem press 3 as described above completes the fabrication of the lamp bulb assembly except for the evacuation and, if desired, gas filling of the lamp bulb 1 which is then carried out in the customary manner through the exhaust tube 10 and the exhaust passageway 8 through the stern press, following which the exhaust tube is then sealed or tipped-01f in the usual manner, as indicated at 22 in Figs. 1 and 2, to thereby hermetically seal the lamp bulb 1 and complete the'manufacture of the lamp according to the invention.

Instead of forming the hook 13 on the supplementary filament support member 12 after the fusion of the latter to the end of the exhaust tube 10 and after the positioning of the lead-in conductors 4 in the supporting jig 15 and the positioning and attachment of the filament 7 in place on the lead-in conductors 4, the said hook 13 may be formed on the support member 12 before the fusion thereof to the end of the exhaust tube 10. In such case, the filament 7 may be engaged within the hook 13 of the support member 12 either at the time the filament is mounted in place on the ends of the lead-in conductors 4, or at the time an assembled pair of conductors 4 and filament '7 is placed in the jig 15.

in he alternative method disclosed in Figs. 8-12, the end of the exhaust tube '10 which is provided with the internal coating 11 first heated and softened, and then upset to form a glass bead 23 in which the supplementary filament support member 12 is thereafter embedded to support it in place on the said end of the exhaust tube, as shown in Fig. 9. A side exhaust opening 24 is then formed in the wall of the exhaust tube 10, at a point immediately below the glass head 23, by directing a gas fire 25 (Fig. against a localized region of the exhaust tube wall and introducing compressed air into the open end of the exhaust tube, after the glass becomes softened, to blow out the said opening 24 in the exhaust tube wall. The assembled exhaust tube 10 and support member 12 shown in Fig. 10 is then placed in the support jig and the lamp then completed in the same manner as described previously except that the exhaust tube 10 is located at a somewhat higher elevation than before (as shown in Fig. 11) sufficient to insure the location of the exhaust aperture 24 in the finished lamp at a point above the stem press 3 thereof as shown in Fig. 12 so as to enable the subsequent evacuation and, if desired, gas filling of the bulb 1 through the exhaust tube 10.

From the foregoing, it will be evident that I have provided a simple and inexpensive way of manufacturing an electric incandescent lamp of the external stem press type having a supplementary support for the filament thereof, which method not only aEords a simplified lamp mount construction but also avoids the objection of a separate insulative bridge member or an objectionably large size glass bead for supporting the supplementary filament support member in place within the bulb.

Although a preferred embodiment of my invention has been disclosed, it will be understood that the invention is not to be limited to the specific construction and arrangement of parts shown, but that they may be widely modified within the spirit and scope of my invention as defined by the appended claim.

What I claim as new and desire to secure by Letters Patent of the United States is:

An electric incandescent lamp comprising a sealed glass envelope having an outwardly protruding external stem press'consisting of the fused mass of glass of a neck portion of said envelope and a glass exhaust tube extending thereinto, said stem press having an exhaust passageway extending therethrough and closed at its outer end, outwardly of said stem press, by a tipped-off residue of said exhaust tube,lead-in conductors sealed through said stem press and extending into said envelope, a filament in said envelope connected to said lead-in conductors, and a supplementary filament support member in said envelope having one end embedded and anchored in the fused glass mass of said stem press and supporting said filament at a point intermediate its connections to said lead-in conductors, the said support member terminating wholly within said stem press and being supported solely thereby.

References Cited in the file of this patent UNITED STATES PATENTS 263,011 Bernstein Aug. 22, 1882 686,218 Forst Nov. 5, 1901 805,282 Germani Nov. 21, 1905 1,247,068 Benbow Nov. 20, 1917 1,569,216 Dake Jan. 12, 1926 1,722,176 Cartun July 23, 1929 1,745,181 Mischler Jan. 28, 1930 1,871,366 Gustin Aug. 9, 1932 2,300,997 Van Horn Nov. 3, 1942 2,351,530 McGowan June 13, 1944 2,447,158 Cartun Aug. 17, 1948 2,496,303 Morse et a1 Feb. 27, 1950 

